In light-water nuclear power stations various circuits exist which convey fluid at high pressure and temperature. Safety conditions prescribe that these circuits preserve the integrity of their operation with respect both to themselves and to the destruction which they can cause to neighboring installations. This integrity of operation must be assured not only for normal conditions of operation, but also for emergency conditions.
In general, connections of supporting members by welding onto piping generate residual stresses which become added to those due to the internal pressure, to expansions and to accidental forces. The elimination of such connections is desirable, more especially as obligatory inspection of them in service involves a supplementary charge.
Various types of connections of fixed point type between piping and a support are known. A usual device includes an intermediate piece welded to the wall of the piping and fixed by welding or bolting to a supporting structure capable of absorbing the forces.
Another device includes a U-shaped collar which surrounds the piping and which is fixed to a stirrup integral with the supporting structure. Blocks welded to the piping on opposite sides of the collar assure the immobilization of the piping.
Other devices described, for example, in French Patent Nos. 2,300,287 and 2,301,764 comprise a sleeve or a double annular sleeve which surrounds the piping. This sleeve is connected to the pipwork by a welded crown and is anchored in the wall through which the piping passes. This device assures anchorage in the wall as well as thermal insulation.
Other devices such as that described in French Pat. No. 2,317,736 includes a conical crown surrounding the piping to which it is attached by way of a reinforced piece of the piping. This crown is fixed at its outer periphery to a supporting structure. This design tolerates small angular deviations of the piping.
Another fixed point device for piping is disclosed in French Pat. No. 2,327,477. It comprises a disc which surrounds the piping to which it is welded, and is housed in a hollow crown fixed to the supporting structure.
The prior art devices are satisfactory for absorbing the axial forces or the forces in shear. In order to absorb the forces of torsion or bending, these devices must be combined with abutments where high stress levels in the connecting welds to the piping must be allowed.